Liquid-Crystal Medium

ABSTRACT

The invention relates to a liquid-crystalline medium based on a mixture of polar compounds which comprises at least one compound of the formula I 
     
       
         
         
             
             
         
       
         
         
           
             in which 
             R 11 , R 12 , A 1 , A 2 , Z 1 , Z 2 , m and n have the meanings indicated in claim  1,  and to the use thereof for an active-matrix display based on the ECB, PALC or IPS effect.

The invention relates to a liquid-crystalline medium based on a mixtureof polar compounds which comprises at least one compound of the formulaI

-   -   in which    -   R¹¹ and R¹² each, independently of one another, denote H, an        alkyl or alkenyl radical having up to 15 C atoms which is        unsubstituted, monosubstituted by CN or CF₃ or at least        monosubstituted by halogen, where, in addition, one or more CH₂        groups in these radicals may be replaced by —O—, —S—,

—C≡C—, —OC—O— or —O—CO— in such a way that O atoms are not linkeddirectly to one another,

-   -   A¹ and A² each, independently of one another, denote        -   a) a 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in            which one or two non-adjacent CH₂ groups may be replaced by            —O— or —S—,        -   b) a 1,4-phenylene radical, in which one or two CH groups            may be replaced by N,        -   c) a radical from the group consisting of            piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene,            naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl,            1,2,3,4-tetrahydronaphthalene-2,6-diyl,            phenanthrene-2,7-diyl and fluorene-2,7-diyl,            -   where the radicals a), b) and c) may be monosubstituted                or polysubstituted by halogen atoms,    -   Z¹ and Z² each, independently of one another, denote —CO—O—,        —O—CO—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CH₂CH₂—, —(CH₂)₄—,        —C₂F₄—, —CH₂CF₂—, —CF₂CH₂—, —CF═CF—, —CH═CF—, —CF═CH—, —CH═CH—,        —C≡C— or a single bond, and    -   m and n each, independently of one another, denote 0,1 or 2.

Media of this type are to be used, in particular, for electro-opticaldisplays with active-matrix addressing based on the ECB effect and forIPS (in plane switching) displays. The medium according to the inventionpreferably has negative dielectric anisotropy.

The principle of electrically controlled birefringence, the ECB(electrically controlled birefringence) effect or DAP (deformation ofaligned phases) effect, was described for the first time in 1971 (M. F.Schieckel and K. Fahrenschon, “Deformation of nematic liquid crystalswith vertical orientation in electrical fields”, Appl. Phys. Lett. 19(1971), 3912). Papers by J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193)and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869) followed.

The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers(1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82Digest Techn. Papers (1 982), 244) have shown that liquid-crystallinephases must have high values for the ratio between the elastic constantsK₃/K₁, high values for the optical anisotropy An and values for thedielectric anisotropy Δε of ≦−0.5 in order to be suitable for use inhigh-information display elements based on the ECB effect.Electro-optical display elements based on the ECB effect have ahomeotropic edge alignment. Dielectrically negative liquid-crystal mediacan also be used in displays which use the so-called IPS effect.Industrial application of this effect in electro-optical displayelements requires LC phases which have to satisfy a multiplicity ofrequirements. Particularly important here are chemical resistance tomoisture, air and physical influences, such as heat, radiation in theinfrared, visible and ultraviolet regions, and direct and alternatingelectric fields.

Furthermore, LC phases which can be used industrially are required tohave a liquid-crystalline mesophase in a suitable temperature range andlow viscosity.

None of the series of compounds having a liquid-crystalline mesophasethat have been disclosed hitherto includes a single compound which meetsall these requirements. Mixtures of two to 25, preferably three to 18,compounds are therefore generally prepared in order to obtain substanceswhich can be used as LC phases. However, it has not been possible toprepare optimum phases easily in this manner, since no liquid-crystalmaterials having significantly negative dielectric anisotropy andadequate long-term stability have hitherto been available.

Matrix liquid-crystal displays (MLC displays) are known. Non-linearelements which can be used for individual switching of the individualpixels are, for example, active elements (i.e. transistors). The term“active matrix” is then used, where a distinction can be made betweentwo types:

-   -   1. MOS (metal oxide semiconductor) transistors on a silicon        wafer as substrate.    -   2. Thin-film transistors (TFTs) on a glass plate as substrate.

In the case of type 1, the electro-optical effect used is usuallydynamic scattering or the guest-host effect. The use of single-crystalsilicon as substrate material restricts the display size, since evenmodular assembly of various part-displays results in problems at thejoints.

In the case of the more promising type 2, which is preferred, theelectro-optical effect used is usually the TN effect.

A distinction is made between two technologies: TFTs comprising compoundsemiconductors, such as, for example, CdSe, or TFTs based onpolycrystalline or amorphous silicon. The latter technology is beingworked on intensively worldwide.

The TFT matrix is applied to the inside of one glass plate of thedisplay, while the other glass plate carries the transparentcounterelectrode on its inside. Compared with the size of the pixelelectrode, the TFT is very small and has virtually no adverse effect onthe image. This technology can also be extended to fully colour-capabledisplays, in which a mosaic of red, green and blue filters is arrangedin such a way that a filter element is opposite each switchable pixel.

The TFT displays disclosed hitherto usually operate as TN cells withcrossed polarisers in transmission and are back-lit.

The term MLC displays here covers any matrix display with integratednonlinear elements, i.e. besides the active matrix, also displays withpassive elements, such as varistors or diodes(MIM=metal-insulator-metal).

MLC displays of this type are particularly suitable for TV applications(for example pocket TVs) or for high-information displays in automobileor air-craft construction. Besides problems regarding the angledependence of the contrast and the response times, difficulties alsoarise in MLC displays due to insufficiently high specific resistance ofthe liquid-crystal mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H.,YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H.,Proc. Eurodisplay 84, September 1984: A 210-288 Matrix LCD Controlled byDouble Stage Diode Rings, pp. 141 ff., Paris; STROMER, M., Proc.Eurodisplay 84, September 1984: Design of Thin Film Transistors forMatrix Addressing of Television Liquid Crystal Displays, pp.145 ff.,Paris]. With decreasing resistance, the contrast of an MLC displaydeteriorates. Since the specific resistance of the liquid-crystalmixture generally drops over the life of an MLC display owing tointeraction with the inside surfaces of the display, a high (initial)resistance is very important for displays that have to have acceptableresistance values over a long operating period.

The disadvantage of the MLC-TN displays disclosed hitherto is due totheir comparatively low contrast, the relatively high viewing-angledependence and the difficulty of producing grey shades in thesedisplays.

There thus continues to be a great demand for MLC displays having veryhigh specific resistance at the same time as a wideoperating-temperature range, short response times and low thresholdvoltage with the aid of which various grey shades can be produced.

The invention has the object of providing MLC displays, in particularfor monitor and TV applications, which are based on the ECB or IPSeffect and do not have the disadvantages indicated above, or only do soto a lesser extent, and at the same time have very high specificresistance values.

It has now been found that this object can be achieved if nematicliquid-crystal mixtures which comprise at least one compound of theformula I are used in these display elements.

The invention thus relates to a liquid-crystalline medium based on amixture of polar compounds which comprises at least one compound of theformula I.

Compounds of the formula I are known, for example, from DE 195 00 768C2, where they are preferably employed in ferroelectric phases. The useof fluorinated phenanthrenes of the formula I for active-matrixapplications, in particular for ECB or IPS displays, is not known.

The mixtures according to the invention exhibit very favourable valuesfor the capacitive threshold, relatively high values for the holdingratio and at the same time very good low-temperature stability as wellas very low rotational viscosities. The mixtures according to theinvention are furthermore distinguished by a good ratio of clearingpoint and rotational viscosity and a high negative dielectricanisotropy.

Some preferred embodiments of the mixtures according to the inventionare shown below:

-   -   a) R¹¹ and/or R¹² in the compounds of the formula I preferably        denote H, alkyl, alkenyl or alkoxy having up to 6 C atoms; R¹¹        and R¹² particularly preferably denote alkyl, where the alkyl        radical may be identical or different.    -   b) Liquid-crystalline medium which additionally comprises one or        more compounds of the formulae IIA and/or IIB

-   -   -   in which        -   R² has the meaning indicated for R¹¹,        -   p denotes 1 or 2, and        -   v denotes 1 to 6.

    -   c) Liquid-crystalline medium which additionally comprises one or        more compounds of the formula III

-   -   -   in which        -   R³¹ and R³² each, independently of one another, denote a            straight-chain alkyl, alkylalkoxy or alkoxy radical having            up to 12 C atoms, and

-   -   d) Liquid-crystalline medium which comprises one, two, three,        four or more, preferably one or two, compounds of the formula I.    -   e) Liquid-crystalline medium in which R¹¹ in the formula I        preferably has the following meanings: straight-chain alkyl,        vinyl, 1E-alkenyl or 3-alkenyl.        -   If R¹ denotes alkenyl, it preferably denotes CH₂═CH,            CH₃—CH═CH, C₃H₇—CH═CH, CH₂═CH—C₂H₅ or CH₃—CH═CH—C₂H₅.    -   f) Liquid-crystalline medium in which the proportion of        compounds of the formula I in the mixture as a whole is at least        3% by weight, preferably at least 10% by weight.    -   g) Liquid-crystalline medium in which the proportion of        compounds of the formulae IIA and/or IIB in the mixture as a        whole is at least 20% by weight.    -   h) Liquid-crystalline medium in which the proportion of the        compounds of the formula III in the mixture as a whole is at        least 5% by weight.    -   i) Liquid-crystalline medium which comprises at least one        compound selected from the sub-formulae I1 to I38:

Particularly preferred media comprise one or more compounds selectedfrom the group consisting of the compounds of the formulae

-   -   j) Liquid-crystalline medium which additionally comprises one or        more compounds selected from the formulae IIIa to IIIf:

-   -   -   in which        -   alkyl and        -   alkyl* each, independently of one another, denote a            straight-chain alkyl radical having 1-6 C atoms, and        -   alkenyl and        -   alkenyl* each, independently of one another, denote a            straight-chain alkenyl radical having 2-6 C atoms.

The medium according to the invention preferably comprises at least onecompound of the formula IIIa, formula IIIb and/or formula IIIe.

Particularly preferred compounds of the formulae IIIe and IIIf are shownbelow:

-   -   k) Liquid-crystalline medium which essentially comprises or        consists of:        -   5-30% by weight of one or more compounds of the formula I            and        -   20-70% by weight of one or more compounds of the formulae            IIA and/or IIB.    -   l) Liquid-crystalline medium which additionally comprises one or        more tetracyclic compounds of the formulae

-   -   -   in which        -   R⁷ and R⁸ each, independently of one another, have one of            the meanings indicated for R¹¹ in claim 1, and        -   w and x each, independently of one another, denote 1 to 6.

    -   m) Liquid-crystalline medium which additionally comprises one or        more compounds of the formulae

-   -   -   in which R¹³-R²⁸ each, independently of one another, have            the meaning indicated for R¹¹, and z and m each,            independently of one another, denote 1-6. R^(E) denotes H,            CH₃, C₂H₅ or n-C₃H₇.

    -   n) Liquid-crystalline medium which additionally comprises one or        more compounds of the formula

-   -   -   preferably in amounts of >3% by weight, in particular ≧5% by            weight and very particularly preferably 5-25% by weight,        -   where        -   R²⁹ has the meanings indicated for R¹¹ and m denotes 1-6.

    -   o) Liquid-crystalline medium additionally comprising one or more        compounds of the formulae

-   -   -   in which R denotes alkyl, alkenyl, alkoxy, alkylalkoxy or            alkenyloxy having 1 or 2 to 6 C atoms, and alkenyl has the            meaning indicated above.

    -   p) Liquid-crystalline medium which additionally comprises one or        more compounds of the formulae

-   -   -   preferably in amounts of >3% by weight, in particular ≧5% by            weight and very particularly preferably 5-25% by weight,        -   where        -   R³⁰⁻³¹ has the meanings indicated for R¹¹ and R32 denotes            CH₃, C₂H₅ or n-C₃H₇.

    -   q) Liquid-crystalline medium which additionally comprises one or        more compounds of the formulae

-   -   -   in which R^(N1) to R^(N10) each, independently of one            another, have the meanings indicated for R¹¹, and the            proportion of the naphthylene compounds in the mixture is            2-40% by weight, based on the mixture.

The invention furthermore relates to an electro-optical display withactive-matrix addressing based on the ECB effect, characterised in thatit contains, as dielectric, a liquid-crystalline medium according to oneof claims 1 to 9.

The liquid-crystal mixture preferably has a nematic phase range of atleast 60 K and a flow viscosity ν₂₀ of at most 30 mm² s⁻¹ at 20° C.

The liquid-crystal mixture according to the invention has a Δε of about−0.5 to −8.0, in particular about −3.0 to −6.0, where Δε denotes thedielectric anisotropy. The rotational viscosity γ₁ is preferably <150mPa·s, in particular <140 mPa·s.

The birefringence Δn in the liquid-crystal mixture is generally between0.07 and 0.16, preferably between 0.08 and 0.11.

The mixtures according to the invention are suitable for all VA-TFTapplications, such as, for example, VAN, MVA, PVA and ASV. They arefurthermore suitable for IPS and PALC applications of negative Δε.

The compounds of the formula I can be prepared, for example, as follows:

The nematic liquid-crystal mixtures in the displays according to theinvention generally comprise two components A and B, which themselvesconsist of one or more individual compounds.

Component A has significantly negative dielectric anisotropy and givesthe nematic phase a dielectric anisotropy of ≦−0.5. It preferablycomprises compounds of the formulae I, IIA and/or IIB.

The proportion of component A is preferably between 45 and 100%, inparticular between 60 and 100%.

For component A, one (or more) individual compound(s) which has (have) avalue of Δε of ≦−0.8 is (are) preferably selected. This value must bemore negative the smaller the proportion A in the mixture as a whole.

Component B has pronounced nematogeneity and a flow viscosity of notgreater than 30 mm²·s⁻¹, preferably not greater than 25 mm²·s⁻¹, at 20°C.

Particularly preferred individual compounds in component B are extremelylow-viscosity nematic liquid crystals having a flow viscosity of notgreater than 18 mm²·s⁻¹, preferably not greater than 12 mm²·s⁻¹, at 20°C.

Component B is monotropically or enantiotropically nematic, has nosmectic phases and is able to prevent the occurrence of smectic phasesdown to very low temperatures in liquid-crystal mixtures. For example,if various materials of high nematogeneity are added to a smecticliquid-crystal mixture, the nematogeneity of these materials can becompared through the degree of suppression of smectic phases that isachieved.

A multiplicity of suitable materials is known to the person skilled inthe art from the literature. Particular preference is given to compoundsof the formula III.

In addition, these liquid-crystal phases may also comprise more than 18components, preferably 18 to 25 components.

The phases preferably comprise 4 to 15, in particular 5 to 12, compoundsof the formulae I, IIA and/or IIB and optionally III.

Besides compounds of the formulae I, IIA and/or IIB and III, otherconstituents may also be present, for example in an amount of up to 45%of the mixture as a whole, but preferably up to 35%, in particular up to10%.

The other constituents are preferably selected from nematic ornematogenic substances, in particular known substances, from the classesof the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenylor cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates,phenylcyclohexanes, cyclohexylbiphenyls, cyclohexylcyclohexanes,cyclohexylnaphthalenes, 1,4-biscyclohexylbiphenyls orcyclohexylpyrimidines, phenyl- or cyclohexyldioxanes, optionallyhalogenated stilbenes, benzyl phenyl ethers, tolans and substitutedcinnamic acid esters.

The most important compounds which are suitable as constituents ofliquid-crystal phases of this type can be characterised by the formulaIV

R⁹-L-G-E-R¹⁰   IV

in which L and E each denote a carbocyclic or heterocyclic ring systemfrom the group formed by 1,4-disubstituted benzene and cyclohexanerings, 4,4′-disubstituted biphenyl, phenylcyclohexane andcyclohexylcyclohexane systems, 2,5-disubstituted pyrimidine and1,3-dioxane rings, 2,6-disubstituted naphthalene, di- andtetrahydronaphthalene, quinazoline and tetrahydroquinazoline,

G denotes —CH═CH— —N(O)═N— —CH-CQ— —CH═N(O)— —C≡C— —CH₂—CH₂— —CO—O——CH₂—O— —CO—S— —CH₂—S— —CH═N— —COO-Phe-COO— —CF₂O— —CF═CF— —OCF₂— —OCH₂——(CH₂)₄— —(CH₂)₃O—or a C—C single bond, Q denotes halogen, preferably chlorine, or —CN,and R⁹ and R¹⁰ each denote alkyl, alkenyl, alkoxy, alkanoyloxy oralkoxycarbonyloxy having up to 18, preferably up to 8, carbon atoms, orone of these radicals alternatively denotes CN, NC, NO₂, NCS, CF₃, OCF₃,F, Cl or Br.

In most of these compounds, R⁹ and R¹⁰ are different from one another,one of these radicals usually being an alkyl or alkoxy group. Othervariants of the proposed substituents are also common. Many suchsubstances or also mixtures thereof are commercially available. Allthese substances can be prepared by methods known from the literature.

It goes without saying for the person skilled in the art that the VA,IPS or PALC mixture according to the invention may also comprisecompounds in which, for example, H, N, O, Cl and F have been replaced bythe corresponding isotopes.

The construction of the liquid-crystal displays according to theinvention corresponds to the usual geometry, as described, for example,in EP-A 0 240 379.

The following examples are intended to explain the invention withoutlimiting it. Above and below, percentages are per cent by weight; alltemperatures are indicated in degrees Celsius.

Besides the compounds of the formula I, the mixtures according to theinvention preferably comprise one or more of the compounds shown below.

The following abbreviations are used:

The liquid-crystal mixtures which can be used in accordance with theinvention are prepared in a manner which is conventional per se. Ingeneral, the desired amount of the components used in lesser amount isdissolved in the components making up the principal constituent,advantageously at elevated temperature. It is also possible to mixsolutions of the components in an organic solvent, for example inacetone, chloroform or methanol, and to remove the solvent again, forexample by distillation, after thorough mixing.

The dielectrics may also comprise further additives known to the personskilled in the art and described in the literature, such as, forexample, UV absorbers, antioxidants and free-radical scavengers. Forexample, 0-15% of pleochroic dyes, stabilisers or chiral dopants may beadded.

For example, 0-15% of pleochroic dyes may be added, furthermoreconductive salts, preferably ethyldimethyldodecylammonium4-hexoxybenzoate, tetrabutylammonium tetraphenylboranate or complexsalts of crown ethers (cf., for example, Haller et al., Mol. Cryst. Liq.Cryst. Volume 24, pages 249-258 (1973)) in order to improve theconductivity or substances may be added in order to modify thedielectric anisotropy, the viscosity and/or the alignment of the nematicphases. Substances of this type are described, for example, in DE-A 2209 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53728.

Table A shows possible dopants which can be added to the mixturesaccording to the invention. If the mixtures comprise a dopant, it isemployed in amounts of 0.01-4% by weight, preferably 0.1-1.0% by weight.

TABLE A

Stabilisers which can be added, for example, to the mixtures accordingto the invention are shown below in Table B.

TABLE B (n = 1-12)

The following examples are intended to explain the invention withoutlimiting it. Above and below,

-   -   V_(o) denotes the threshold voltage, capacitive [V] at 20° C.    -   Δn denotes the optical anisotropy measured at 20° C. and 589 nm    -   Δε denotes the dielectric anisotropy at 20° C. and 1 kHz    -   cp. denotes the clearing point [° C]    -   γ₁ denotes the rotational viscosity measured at 20° C. [mPa·s]    -   LTS denotes the low temperature stability, determined in test        cells

The display used for measurement of the threshold voltage has twoplane-parallel outer plates at a separation of 20 μm and electrodelayers with overlying alignment layers of SE-1211 (Nissan Chemicals) onthe insides of the outer plates, which effect a homeotropic alignment ofthe liquid crystals.

MIXTURE EXAMPLES Example 1

CY-3-O4  3.00% Clearing point [° C.]: 84.5 CY-5-O2  4.00% Δn [589 nm,20° C.]: 0.1299 CCY-3-O3 11.00% ε_(∥) [1 kHz, 20° C.]: 4.0 CPY-2-O212.00% Δε [1 kHz, 20° C.]: −3.8 CPY-3-O2 12.00% V₀ [V]: 2.05 CC-5-V20.00% γ₁ [mPa · s, 20° C.]: 156 CC-3-V1 10.00% LTS cells −20° C.: 1000h CCH-35  2.00% PYP-2-3 10.00% PYP-2-4  6.00%

10.00%

Example 2

CY-3-O4  6.00% Clearing point [° C.]: 87.5 CY-5-O2  3.00% Δn [589 nm,20° C.]: 0.1285 CCY-3-O3 10.00% ε_(∥) [1 kHz, 20° C.]: 3.8 CPY-2-O212.00% Δε [1 kHz, 20° C.]: −3.6 CPY-3-O2 12.00% V₀ [V]: 2.17 CC-5-V20.00% γ₁ [mPa · s, 20° C.]: 152 CC-3-V1 12.00% PYP-2-3 10.00% PYP-2-4 5.00%

10.00%

Example 3

CY-3-O4  3.00% Clearing point [° C.]: 85.0 CY-5-O2  4.00% Δn [589 nm,20° C.]: 0.1296 CCY-3-O3 11.00% ε_(∥) [1 kHz, 20° C.]: 3.8 CPY-2-O212.00% Δε [1 kHz, 20° C.]: −3.8 CPY-3-O2 12.00% V₀ [V]: 2.05 CC-5-V20.00% γ₁ [mPa · s, 20° C.]: 159 CC-3-V1 10.00% CCH-35  2.00% PYP-2-310.00% PYP-2-4  6.00%

10.00%

Example 4

CY-3-O4  7.00% Clearing point [° C.]: 86.0 CCY-3-O3  5.00% Δn [589 nm,20° C.]: 0.1612 CPY-2-O2 12.00% ε_(∥) [1 kHz, 20° C.]: 4.2 CPY-3-O212.00% Δε [1 kHz, 20° C.]: −3.9 CC-5-V 16.00% V₀ [V]: 1.99 CC-3-V1 4.00% γ₁ [mPa · s, 20° C.]: 200 BCH-32  2.00% LTS cells −20° C.: 1000 hPYP-2-3 16.00% PYP-2-4 16.00%

 5.00%

 5.00%

Example 5

CY-3-O4  8.00% Clearing point [° C.]: 79.0 CY-5-O2 12.00% Δn [589 nm,20° C.]: 0.1035 CCY-3-O2 12.00% ε_(∥) [1 kHz, 20° C.]: 4.7 CCY-3-O312.00% Δε [1 kHz, 20° C.]: −6.1 CCY-4-O2 11.00% V₀ [V]: 1.59 CPY-3-O210.00% γ₁ [mPa · s, 20° C.]: 193 CC-4-V 17.00% CCH-34  4.00%

 7.00%

 7.00%

Example 6

CY-3-O2  6.00% Clearing point [° C.]: 79.0 CCY-3-O3 12.00% Δn [589 nm,20° C.]: 0.0918 CCY-4-O2  9.00% ε_(∥) [1 kHz, 20° C.]: 3.7 CPY-2-O211.00% Δε [1 kHz, 20° C.]: −3.3 CPY-3-O2  3.00% V₀ [V]: 2.16 CC-5-V20.00% γ₁ [mPa · s, 20° C.]: 108 CC-3-V1 12.00% CCH-34 6.00% CCH-30311.00%

 5.00%

 5.00%

Example 7

CY-3-O2 17.00% Clearing point [° C.]: 80.5 CCY-3-O2 11.00% Δn [589 nm,20° C.]: 0.0840 CCY-3-O3 12.00% ε_(∥) [1 kHz, 20° C.]: 3.7 CCY-4-O212.00% Δε [1 kHz, 20° C.]: −3.9 CC-5-V 20.00% V₀ [V]: 2.10 CC-3-V111.00% γ₁ [mPa · s, 20° C.]: 116 CCH-34  6.00% CCH-303  4.00%

 4.00%

 3.00%

Example 8

CY-3-O2 15.00% Clearing point [° C.]: 78.0 CCY-3-O2  6.00% Δn [589 nm,20° C.]: 0.0891 CCY-3-O3 12.00% ε_(∥) [1 kHz, 20° C.]: 3.9 CCY-4-O212.00% Δε [1 kHz, 20° C.]: −4.0 CPY-3-O2  4.00% V₀ [V]: 2.04 CC-5-V20.00% γ₁ [mPa · s, 20° C.]: 120 CC-3-V1 12.00% CCH-34  6.00% CCH-303 3.00%

 5.00%

 5.00%

Example 9

CY-3-O2  4.00% Clearing point [° C.]: 80.0 CCY-3-O3 12.00% Δn [589 nm,20° C.]: 0.0879 CCY-4-O2  6.00% Δε [1 kHz, 20° C.]: −3.9 CPY-3-O2 12.00%γ₁ [mPa · s, 20° C.]: 110 CC-5-V 20.00% CC-3-V1 12.00% CCH-34  7.00%CCH-303  7.00%

 5.00%

 5.00%

 5.00%

 5.00%

Example 1 0

CY-3-O2  4.00% Clearing point [° C.]: 79.5 CCY-3-O2 10.00% Δn [589 nm,20° C.]: 0.0901 CCY-3-O3 12.00% Δε [1 kHz, 20° C.]: −3.9 CCY-4-O2 12.00%γ₁ [mPa · s, 20° C.]: 108 CC-5-V 20.00% CC-3-V1 12.00% CCH-34  6.00%CCH-303  4.00%

 5.00%

 5.00% PY-3-O4  5.00% PY-5-O4  5.00%

1. Liquid-crystalline medium based on a mixture of polar compounds,characterised in that it comprises at least one compound of the formulaI

in which R¹¹ and R¹² each, independently of one another, denote H, analkyl or alkenyl radical having up to 15 C atoms which is unsubstituted,monosubstituted by CN or CF₃ or at least monosubstituted by halogen,where, in addition, one or more CH₂ groups in these radicals may bereplaced by —O—, —S—,

—C≡C—, —OC—O— or —O—CO— in such a way that O atoms are not linkeddirectly to one another, A¹ and A² each, independently of one another,denote a)a 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in whichone or two non-adjacent CH₂ groups may be replaced by —O— or —S—, b) a1,4-phenylene radical, in which one or two CH groups may be replaced byN, c) a radical from the group consisting of piperidine-1,4-diyl,1,4-bicyclo[2.2.2]octylene, naphthalene-2,6-diyl,decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl,phenanthrene-2,7-diyl and fluorene-2,7-diyl, where the radicals a), b)and c) may be monosubstituted or polysubstituted by halogen atoms, Z¹and Z² each, independently of one another, denote —CO—O—, —O—CO—,—CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CH₂CH₂—, —(CH₂)₄—, —C₂F₄—, —CH₂CF₂—,—CF₂CH₂—, —CF═CF—, —CH═CF—, —CF═CH—, —CH═CH—, —C≡C— or a single bond,and m and n each, independently of one another, denote 0, 1 or
 2. 2.Liquid-crystalline medium according to claim 1, characterised in that itadditionally comprises one or more compounds of the formulae IIA and/orIIB:

in which R² denotes an alkyl or alkenyl radical having up to 15 C atomswhich is unsubstituted, monosubstituted by CN or CF₃ or at leastmonosubstituted by halogen, where, in addition, one or more CH₂ groupsin these radicals may each be replaced, independently of one another, by—O—, —S—,

—C≡C—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that O atoms arenot linked directly to one another, p denotes 1 or 2, and v denotes 1 to6.
 3. Liquid-crystalline medium according to claim 1, characterised inthat it additionally comprises one or more compounds of the formula III

in which R³¹ and R³² each, independently of one another, denote astraight-chain alkyl, alkenyl, alkylalkoxy or alkoxy radical having upto 12 C atoms, and


4. Liquid-crystalline medium according to claim 1, characterised in thatit comprises one, two, three, four or more compounds of the formula I.5. Liquid-crystalline medium according to claim 1, characterised in thatthe proportion of compounds of the formula I in the mixture as a wholeis at least 3% by weight.
 6. Liquid-crystalline medium according toclaim 1, characterised in that the proportion of compounds of theformulae IIA and/or IIB in the mixture as a whole is at least 20% byweight.
 7. Liquid-crystalline medium according to claim 1, characterisedin that the proportion of compounds of the formula III in the mixture asa whole is at least 3% by weight.
 8. Liquid-crystalline medium accordingto claim 1, characterised in that it comprises at least one compoundselected from the formulae I1 to I38

in which R¹¹ has the meaning indicated in claim 1, and alkyl denotes astraight-chain alkyl radical having 1-6 C atoms.
 9. Liquid-crystallinemedium according to claim 1, characterised in that it essentiallyconsists of 5-30% by weight of one or more compounds of the formula Iand 20-70% by weight of one or more compounds of the formulae IIA and/orIIB.
 10. Electro-optical display with active-matrix addressing based onthe ECB, PALC or IPS effect, characterised in that it contains, asdielectric, a liquid-crystalline medium according to claim 1.